Impregnated material



Patented Mar. 29, 1938 l'lED' STATES @i-FICE 2,112,732 IMPREGNATED MATERIAL Hermann C. Burmeister, Hennigsdori, Germany,

assignor to General Electric Company, Schenectady, N. Y.

No Drawing. Original application July 27, 1934, Serial No. 737,315. Divided and this ap- A plication August 21, 1935, Serial No. 37,185. In Germany July 27, 1933 3 Claims.

'g'Thisi application is a division of my copending application Serial No. 737,315, filed July 27, 1934, and assigned to the same assignee as the present invention.

My invention relates to impregnated materials adapted for use as insulators and more especially to fibrous material impregnated with artificial resins and exposed to the simultaneous.

produced.

The insulating material here in View is impregnated with condensation products obtained by the interaction of aromatic amines and aldehydes. Hitherto such condensation products have been produced by causing 1 mol. of the aromatic amine to react with 1 mol. of an aldehyde in acid'solution. In this reaction is formed a soluble and fusible resin, called lacquer resin, which cannot berendered insoluble and in- ."fusible. If more than 1 mol. .of aldehyde is made to fact on 1 mol. of an aromatic amine, there are formed as a rule products that are insoluble from the beginning and the field of application of which is rather narrow.

impregnated with condensation products of this typejwhich'are soluble, but can be converted into insoluble and infusible products and which,

in contradistinction toithe lacquer resins men- 35 tioned above, can be influenced by heat so that their softening point rises, the impregnated products thus obtained are capable of a far more extended technical application.

According to the present invention the resinous 40 compounds formed in this reaction are caused to polymerize in a suitable solvent, whereby the molecule of the resin isenlarged so that the solution possesses a higher viscosity. If such a solution is then used for impregnating lami- 5 nated material, tissue or the like, the greater viscosity of the solution leads to products which are superior, as far as insulating power is concerned, to similar products produced with ordinary solutions of these resins. I have found that the resinous product obtained by polymerizing the initial condensation product in a. solvent composed for example of benzene and alcohol, to such extent that the resulting composi- 55 ticn has a viscosity of at least 4 Engler at 20 I have now found that if fibrous material is C., owing to its larger molecule, does not penetrate fibrous materials as thoroughly as the ordinary impregnating solutions and, as a result, the innermost fibers are substantially free from resin. In consequence thereof the final products, more especially of laminated material, and which comprise fibrous material (for example, paper) coated and at least partly impregnated with insoluble and infusible resin such as herein described, are particularly pliable and possess great mechanical strength, of even greater importance, from the standpoint ofelectrical applications, possess very high dielectric properties. v

I wish it to be understood that my invention is not limited to the production of laminated material, butincludes as well the production of non-laminated'fibrous or other material which is impregnated with a condensation product of an aromatic amine and an aldehyde, this product having been treated in solution for polymerization and the obtention of a higher degree of viscosity.'

This polymerizing treatment of a. resinous body is carried out preferably in a mixture of benzene and alcohol containing 50-90% benzene and 50 10% alcohol. The resinous body dissolved in this mixture is heated under the reflux condenser. The degree of polymerization can be controlled by viscosity tests. A 40% solution of the resin in the mixture of solvents shows at 20- C. a viscosity of 2 Engler. On being heated to 50-60 C. the viscosity of the solution rises slowly, as shown by determining the Engler viscosity at 20 C. of a sample of the same. The resulting product is a viscous composition consisting essentially of a solvent, composed of benzene and alcohol, and an aromatic amine-aldehyde condensation product polymerized in such solvent. For the purpose of impregnating paper or tissue I prefer using a solution 01 a resin poly=-' 'merized to such extent that the composition has a viscosity of 4-6 Engler at 20 C. With such a solution I obtain a product which is superior to the impregnated materials of a. similar kind hith-' erto knownas regards mechanical strength and resistivity to heat. While laminated material produced by impregnating paper with similar products as hitherto produced is capable of resisting a temperature of about 100-120" C., the heat resistivity of laminated material produced in accordance with the 'present invention can be raised to about 170 C.

In practicing my invention I may proceed, for instance, as follows:

' a plastic viscosity .hoi and the solution is mixed with'about 22.5 kgs.

phthalic acid and 300 kgs. of a 30% formaldehyde solution, 0.25 kg. of a metal chloride such as tin-tetrachloride being added as a contact substance (catalyst). The reaction temperature rises to 48 C. and the mixture is stirred two hours, care being taken to keep the temperature at 48 C. The product of reaction is then allowed to stand about 16 hours. During this time there gradually separates out a thickly fluid resin which, at ordinary temperature, possesses separated from the mother liquor.

This resin, after having been washed with a solution of an alkali to free it from traces of acid and which is insoluble in alcohol, is now dissolved under heating in the mixture of solvents (benzene and alcohol) and heated to 50-60 C. until the viscosity has risen by polymerization to 4-6 Engler at 20 C. In certain cases I may even carry the polymerization still further, that is to say, until the solution has a viscosity at 20 C. above 6 Engler.

For impregnating fillers or webs of fibrous material the solution containing about 40-50% of the resin may be diluted according to the require- Example 2 :93 kgs. aniline are heated under stirring in the water bath to C. together with kgs. glacial acetic acid and 300 liters alcohol. To this mixture.

are added 330 liters-of a 30% aqueous formaldehyde solution. After one hour's stirring at 65 C. the soluble product separates out and can now be treated for polymerization as above described.

Example 3 A similar resinous product is obtained by heating a mixture of 19.6 kgs. hydrochloric acid of 1.19 spec. gr. with 600 kgs. alcohol and 600 kgs. of a 30% aqueous formaldehyde solution to 35C. and adding 186 kgs. aniline under stirring. After one hour's heating to 50 C. the resinous product separates out as a plastic viscous mass, which is now nd which, after settling, is

treated for polymerizationin a suitable mixture of solvents. I

In order to avoid further polymerization during storage of a solution of the resin, the activators present in the resin, such as the acid and the contact substance (catalyst), maybe removed or rendered innocuous by neutralization. I am thus enabled to stabilize against viscosity changes a resinous lacquer of predetermined viscosity. By

.adding acid before using such lacquer for impregnation I can restore its capacity of polymerizing or becoming insoluble or infusible.

Various changes may be made in the details dis closed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

What I claim as 'new and desire to secure by.

benzene and alcohol, and an aromatic aminealdehyde condensation product polymerized in said solvent to such extent that the resulting composition has a viscosity of at least 4 Engler at 20 C., the innermost fibers of said fibrous material being substantially free from said resin.

2. A strong, pliable laminated material of high dielectric strength comprising paper coated and at least partly-impregnated with an insoluble and infuslble resin resulting from a heat and pressure treatment of a viscous composition consisting essentially of a solvent, composed of benzene and alcohol in the proportion of from 50 to 90 per cent benzene to 50 to 10 per cent alcohol, and an aromatic amine-aldehyde condensation product polymerized in said solvent to such extent that the resulting composition has a viscosity of about 4 to 6 Engler at 20 C., the heat resistivity of said laminated material being of the order of about C.

3. Fibrous cellulosic material coated and at least partly impregnated with an insoluble and infusihie resin resulting tromaheat and pressure treatment of a viscous composition havinga viscosity of about 4 to 6 Engler at" 20 C. and comprising a condensation product of an aromatic amine and an aldehyde polymerized in a solvent composed of benzene and alcoholito, the statedvisco'sity, said fibrous material being resistant to a heat as high as about 170 C. i

HERMANN C. BURMEISTER.

CERTIFICATE OF CORRECTION. Patent No. 2,112,732. March 29, 195

HERMANN C 'BURNEISTERV It is hereby certified that error appears in the printed specification,

of the above numbered patent requiring correction as follows Page second column, line 11, before "of" insert the word but; page 2, first column, line 50, for "kgsncm read kgs./cm and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Offiee.

Signed andsealed this 10th day of new, A. D. 19 8.

Henry Van Arsdale,

(Seal) I Actingcommissi oner of Patents. 

